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Obstetrical Anal Sphincter Injuries (OASIS): Prevention, Recognition, and Repair

      Abstract

      Objective

      To review the evidence relating to obstetrical anal sphincter injuries (OASIS) with respect to diagnosis, repair techniques and outcomes. To formulate recommendations as to patient counselling regarding route of delivery for subsequent pregnancy after OASIS.

      Options

      Obstetrical care providers caring for women with OASIS have the option of repairing the anal sphincter using end-to-end or overlapping techniques. They may also be involved in counselling women with prior OASIS regarding the route of delivery for future pregnancies.

      Outcomes

      The outcome measured is anal continence following primary OASIS repair and after subsequent childbirth.

      Evidence

      Published literature was retrieved through searches of Medline, EMBASE, and The Cochrane Library in May 2011 using appropriate controlled vocabulary (e.g., anal canal, obstetrics, obstetric labour complication, pregnancy complication, treatment outcome, surgery, quality of life) and key words (obstetrical anal sphincter injur*, anus sphincter, anus injury, delivery, obstetrical care, surgery, suturing method, overlap, end-to-end, feces incontinence). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational. There were no date or language restrictions. Searches were updated on a regular basis and incorporated in the guideline to September 2014. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

      Values

      The quality of evidence in this document was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table 1).

      Benefits, harms, and costs

      Benefits from implementation of these guidelines include: improved diagnosis of OASIS, optimal functional outcomes following repair, and evidence-based counselling of women for future childbirth

      Key words

      ABBREVIATIONS

      AI
      anal incontinence
      EAS
      external anal sphincter
      IAS
      internal anal sphincter
      NSAID
      non-steroidal anti-inflammatory
      OASIS
      obstetric anal sphincter injuries
      RTC
      randomized control trial
      SVD
      spontaneous vaginal delivery
      WHO
      World Health Organization
      Table 1Key to evidence statements and grading of recommendations, using the ranking of the Canadian Task Force on Preventive Health Care
      Quality of evidence assessment
      The quality of evidence reported in these guidelines has been adapted from The Evaluation of Evidence criteria described in the Canadian Task Force on Preventive Health Care.125
      Classification of recommendations
      Recommendations included in these guidelines have been adapted from the Classification of Recommendations criteria described in the Canadian Task Force on Preventive Health Care.125
      I:Evidence obtained from at least one properly randomized controlled trialA.There is good evidence to recommend the clinical preventive action
      II-1:Evidence from well-designed controlled trials without randomizationB.There is fair evidence to recommend the clinical preventive action
      II-2:Evidence from well-designed cohort (prospective or retrospective) or case–control studies, preferably from more than one centre or research groupC.The existing evidence is conflicting and does not allow to make a recommendation for or against use of the clinical preventive action; however, other factors may influence decision-making
      II-3:Evidence obtained from comparisons between times or places with or without the intervention Dramatic results in uncontrolled experiments (such as the results of treatment with penicillin in the 1940s) could also be included in this categoryD.There is fair evidence to recommend against the clinical preventive action
      E.There is good evidence to recommend against the clinical preventive action
      III:Opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committeesL.There is insufficient evidence (in quantity or quality) to make a recommendation; however, other factors may influence decision-making
      * The quality of evidence reported in these guidelines has been adapted from The Evaluation of Evidence criteria described in the Canadian Task Force on Preventive Health Care.
      • Woolf S.H.
      • Battista R.N.
      • Angerson G.M.
      • Logan A.G.
      • Eel W.
      Canadian Task Force on Preventive Health Care. New grades for recommendations from the Canad ian Task Force on Preventive Health Care.
      Recommendations included in these guidelines have been adapted from the Classification of Recommendations criteria described in the Canadian Task Force on Preventive Health Care.
      • Woolf S.H.
      • Battista R.N.
      • Angerson G.M.
      • Logan A.G.
      • Eel W.
      Canadian Task Force on Preventive Health Care. New grades for recommendations from the Canad ian Task Force on Preventive Health Care.

      Summary Statements

      • 1.
        Obstetrical anal sphincter injuries may lead to significant comorbidities, including anal incontinence, rectovaginal fistula, and pain. (II-2)
      • 2.
        Obstetrical anal sphincter injuries are more commonly associated with forceps deliveries than with vacuum-assisted vaginal deliveries (II-2)
      • 3.
        Obstetrical anal sphincter injuries (OASIS) repair:
        • a.
          Suture-related morbidity is similar at 6 weeks following the use of either polyglactin 2-0 or polydioxanone 3-0 for OASIS repairs (I)
        • b.
          Repair of the internal anal sphincter is recommended as women who demonstrate an internal anal sphincter defect on postpartum ultrasound have more anal incontinence (III)
        • c.
          Repair of the external anal sphincter should include the fascial sheath. An overlapping technique often requires more dissection and mobilization of the sphincter ends and is only possible with full thickness 3b sphincter tears or greater (III)
        • d.
          A persistent defect of the external anal sphincter remote from delivery may increase the risk of worsening symptoms following subsequent vaginal deliveries. (II-2)
      • 4.
        Obstetrical anal sphincter injuries are associated with an increased risk of postpartum urinary retention. (II-2)
      • 5.
        After a successful repair of obstetrical anal sphincter injuries, most women can safely deliver vaginally in a future pregnancy. (III)
      • 6.
        Counselling women about future delivery plans:
        • a.
          The risk of recurrence of an obstetrical anal sphincter injury at a subsequent delivery is 4% to 8%. (II-2)
        • b.
          It was calculated that 2.3 Caesarean sections at the cost of increased maternal risk would be required to prevent one case of anal incontinence in a woman with prior obstetrical anal sphincter injury. (II-2)

      Recommendations

      • 1.
        All women should be carefully examined for perineal or vaginal tears; those with a tear that is more than superficial in depth should have a systematic rectal examination for obstetrical anal sphincter injury prior to repair. (II-2B)
      • 2.
        The World Health Organization classification should be used to classify obstetrical anal sphincter injury. This distinguishes the degree of external sphincter tear (3a: < 50% or 3b: ≥ 50%) and the presence of internal sphincter defects (3c). A button -hole injury is distinct and should be classified separately as such. (III-B)
      • 3.
        In women having a spontaneous vaginal delivery, the rate of obstetrical anal sphincter injury is decreased when the obstetrical care provider slows the fetal head at crowning. (II-2A)
      • 4.
        Episiotomy:
        • a.
          At the time of either a spontaneous vaginal or instrumental delivery, the obstetrical care provider should follow a policy of “restricted” episiotomy (i.e. only if indicated), rather than “liberal” use (i.e. routine), for the prevention of obstetrical anal sphincter injuries. (I-A)
        • b.
          If an episiotomy is deemed indicated, preference for a mediolateral over a midline should be considered (II-2B) The optimal cutting angle appears to be no less than 45 degrees, ideally around 60 degrees (II-2B)
      • 5.
        Repair can be delayed for 8 to 12 hours with no detrimental effect. Delay may be required so a more experienced care provider is available for the repair. (I-A)
      • 6.
        Prophylactic single dose intravenous antibiotics (2nd generation cephalosporin, e.g. cefotetan or cefoxitin) should be administered for the reduction of perineal wound complications following the repair of obstetrical anal sphincter injury. (I-A)
      • 7.
        Laxatives (e.g., lactulose) should be prescribed following the primary repair of obstetrical anal sphincter injury as they are associated with earlier and less painful first bowel motions and earlier discharge from hospital. Constipating agents and bulking agents are not recommended. (I-A)
      • 8.
        Non-steroidal anti-inflammatories and acetaminophen are the first-line analgesics. Opioids should only be used with caution. Constipation should be avoided by using a laxative or stool softener. (I-A)
      • 9.
        Following obstetrical anal sphincter injury, providers should disclose to women the degree of injury and arrange follow-up. Detailed documentation of the injury and its repair is required. (III-L)
      • 10.
        Women with anal incontinence following obstetrical anal sphincter injury should be referred for pelvic floor physiotherapy. (I-A)

      INTRODUCTION

      While maternal mortality related to childbirth is now rare in the developed world, there continues to be significant maternal morbidity—including that related to the pelvic floor function. A group of women who are at risk of pelvic floor dysfunction following delivery include those in whom the anal sphincter is disrupted during childbirth.

      Definitions

      Perineal trauma occurs either spontaneously with vaginal delivery or secondarily as an extension to an episiotomy. Severe perineal trauma can involve damage to the anal sphincters and anal mucosa. Obstetric anal sphincter injuries include third and fourth degree perineal tears. Third degree tears involve a partial or complete disruption of the anal sphincter complex which includes the external anal sphincter and the internal anal sphincter. Fourth degree tears involve disruption of the anal mucosa in addition to division of the anal sphincter complex.

      Clinical Impact

      OASIS can have a significant impact on women by impairing their quality of life in both the short and long term. One of the most distressing immediate complications of perineal injury is perineal pain. Short-term perineal pain is associated with edema and bruising, which can be the result of tight sutures, infection, or wound breakdown. Perineal pain can lead to urinary retention and defecation problems in the immediate postpartum period. In the long term, women with perineal pain may have dyspareunia and altered sexual function. Additionally, complications of severe perineal tears include abscess formation, wound breakdown, and rectovaginal fistulae.
      Injury to the anal sphincter is recognized as the most common cause of anal incontinence and anorectal symptoms in otherwise healthy women. Obstetrical sphincter injuries have a variety of long-term complications of which anal incontinence is the most distressing and disabling. Anal incontinence incorporates a range of symptoms including: flatal incontinence, passive soiling, or incontinence of liquid or solid stool.
      • Haylen B.T.
      • de Ridder D.
      • Freeman R.M.
      • Swift S.E.
      • Berghmans B.
      • Lee J.
      • et al.
      An International Urogynecological Association (IUGA)/ International Continence Society (ICS) joint report on the terminology for female pelvic floor dysfunction.
      Fecal urgency can also be a symptom experienced by many women. Any of these symptoms can potentially be a hygienic, social, and psychological problem for women. Women are not always forthcoming with symptoms of anal incontinence either due to embarrassment or they feel that the symptoms are a normal result of vaginal delivery.
      The true prevalence of AI related to OASIS may be underestimated. The reported rates of AI following the primary repair of OASIS range between 15% and 61%, with a mean of 39%.
      • Sultan A.H.
      • Kettle C.
      Diagnosis of perineal trauma.
      This high prevalence highlights the need to ensure our surgical techniques and postoperative management are optimal.
      Sustaining an OASIS can have a significant impact on a women’s physical and emotional health. There are personal costs to the patient with pad use and missed time from work, and costs to women and the health care system including appointments and treatments. It may also make women apprehensive about future childbirth and adversely affect the remainder of their reproductive lives. Missed tears or inadequate repair may also present a potential source for litigation.
      Obstetrical trauma that can lead to AI includes structural damage to the anal sphincter complex, pudendal neuropathy (by direct compression or stretching), or both. Despite sphincter repairs, some women may have residual defects and AI symptoms. The onset of symptoms of AI may occur immediately or several years after delivery; anal incontinence may only appear in old age, when the aging process adds to the delivery insult.

      Summary Statement

      • 1.
        Obstetrical anal sphincter injuries lead to significant comorbidities, including anal incontinence, rectovaginal fistula, and pain. (II-2)

      DIAGNOSIS OF OASIS

      Careful examination of the perineum, including a rectal examination for those with a tear that is more than superficial in depth, should be performed in all women prior to suturing.
      • Sultan A.H.
      • Thakar R.
      Third and fourth degree tears.
      Formal training in the recognition of OASIS improves the detection of such injuries,
      • Andrews V.
      • Thakar R.
      • Sultan A.H.
      Structured hands-on training in repair of obstetric anal sphincter injuries (OASIS): an audit of clinical practice.
      as incident rises from 11% to 24.5% when the obstetrical care provider’s examination was repeated by a trained fellow.
      • Andrews V.
      • Sultan A.H.
      • Thakar R.
      • Jones P.W.
      Occult anal sphincter injuries—myth or reality?.
      The inspection should be done with adequate lighting and analgesia and include:
      • inspection of perineum with labial parting,
      • inspection of the distal (caudal) posterior vagina, and
      • inspection for a third degree tear behind an “intact perineum.”
      Palpation is best done
      • Sultan A.H.
      • Thakar R.
      Third and fourth degree tears.
      with the examiner’s dominant index inserted in the anus, and the ipsilateral thumb in the vagina. The 2 fingers then palpate with a “pill-rolling” motion to assess thickness.
      When the external sphincter tears, the ends retract and a cavity is often palpated along the course of the sphincter muscle. This may be less evident in the presence of an epidural.
      Special attention should then be given to the IAS. The IAS is a continuation of the circular smooth muscle of the rectum. This muscle appears pale (like raw white fish), is not very thick, and can be found 6 to 8 mm above (cephalad to) the anal margin (Figure 1; for a more detailed illustration, see online eFigure 1). Examination of the IAS will also permit detection of a button-hole injury.

      Recommendation

      • 1.
        All women should be carefully examined for perineal or vaginal tears; those with a tear that is more than superficial in depth should have a systematic rectal examination for obstetrical anal sphincter injury prior to repair. (II-2B)

      GRADING OF SEVERITY

      Traditionally, the severity of perineal tear was limited to 4 grades: grade 1 (superficial vaginal and/or perineal skin), grade 2 (vaginal muscles), grade 3 (in or through external anal sphincter muscle), and grade 4 (external and internal anal sphincters and anorectal lumen).
      • Cunningham F.
      • Leveno K.J.
      • Bloor S.
      • Hauth J.
      • Rouse D.J.
      • Spong C.
      Normal labor and delivery.
      As there was a lack of consistency in the classification of a partial anal sphincter, with up to 33% of consultant obstetricians classifying a complete or partial tear of the EAS as a second degree tear,
      • Fernando R.J.
      • Sultan A.H.
      • Radley S.
      • Jones P.W.
      • Johanson R.B.
      Management of obstetric anal sphincter injury: a systematic review & national practice survey.
      Sultan
      • Sultan A.H.
      Obstetrical perineal injury and anal incontinence.
      devised a more specific classification, later adopted by the WHO
      • Thach T.
      Methods of repair for obstetric anal sphincter injury: RHL commentary.
      and the International Consultation on Incontinence.
      • Koelbl H.
      • Nitti V.
      • Baessler K.
      • Salvatore S.
      • Sultan A.
      • Yamaguchi O.
      Pathophysiology of urinary incontinence, faecal incontinence and pelvic organ prolapse.
      In this classification, grade 3 is further refined as involving the anal sphincter complex and is divided into 3a, 3b, 3c (Table 2).
      Table 2Classification of OASIS
      First degreeInjury to perineal skin only
      Second degreeInjury to perineum involving perineal muscles but not involving the anal sphincter
      Third degreeInjury to perineum involving the anal sphincter complex:
       3a Less than 50% of EAS thickness torn
       3b More than 50% of EAS thickness torn
       3c Both EAS and IAS torn
      Fourth degreeInjury to perineum involving the anal sphincter complex (EAS and IAS) and anal epithelium
      The type of third degree tear seems to have an impact on symptoms, with OASIS grade 3a and 3b having a better prognosis than 3c. In fact, those with a 3c OASIS had symptoms similar in severity to those with a fourth degree laceration.
      • Roos A.M.
      • Thakar R.
      • Sultan A.H.
      Outcome of primary repair of obstetric anal sphincter injuries (OASIS): does the grade of tear matter?.
      A button-hole injury, where only the vaginal and rectal mucosa are involved, should not be reported as a third or fourth degree tear if found in isolation. Documentation of the presence or absence of a tear, as evidenced on rectal examination, should be disclosed to the patient and incorporated into the delivery note, and repair should be done to avoid fistulization.
      Such a grading system takes into account the degree of tearing experienced by the external sphincter separately from that of the internal sphincter. Such distinction is meant to improve reporting, guide repair, and facilitate outcome research.

      Recommendation

      • 2.
        The World Health Organization classification should be used to classify obstetrical anal sphincter injury. This distinguishes the degree of external sphincter tear (3a: < 50% or 3b: ≥ 50%) and the presence of internal sphincter defects (3c). A button-hole injury is distinct and should be classified separately as such. (III-B)

      EPIDEMIOLOGY OF OASIS

      The incidence of OASIS may vary according to many variables including use of any type of episiotomy (lateral, mediolateral, or midline), type of delivery (spontaneous or assisted vaginal), and type of instrument used (vacuum or forceps); parity, type of obstetrical care provider, and race.
      Overall, studies looking at the incidence of OASIS based on the WHO’s International Classification of Diseases
      • World Health Organization
      report an incidence of 4% to 6.6% of all vaginal birth,
      • Baghestan E.
      • Bordahl P.E.
      • Rasmussen S.A.
      • Sande A.K.
      • Lyslo I.
      • Solvang I.
      A validation of the diagnosis of obstetric sphincter tears in two Norwegian databases, the Medical Birth Registry and the Patient Administration System.
      • Laine K.
      • Gissler M.
      • Pirhonen J.
      Changing incidence of anal sphincter tears in four Nordic countries through the last decades.
      • Sultan A.H.
      • Kamm M.A.
      • Hudson C.N.
      • Thomas J.M.
      • Bartram C.I.
      Anal-sphincter disruption during vaginal delivery.
      • Fretheim A.
      • Odgaard-Jensen J.
      • Rottingen J.A.
      • Reinar L.M.
      • Vangen S.
      • Tanbo T.
      The impact of an intervention programme employing a hands-on technique to reduce the incidence of anal sphincter tears: interrupted time-series reanalysis.
      with higher rates in assisted deliveries (6%) than in SVD (5.7%).
      • Ekeus C.
      • Nilsson E.
      • Gottvall K.
      Increasing incidence of anal sphincter tears among primiparas in Sweden: a population-based register study.
      An OASIS is often misdiagnosed at the time of delivery by obstetrical care providers. One study reported that the overall rate of missed OASIS ranged from 26% to 87%.
      • Andrews V.
      • Sultan A.H.
      • Thakar R.
      • Jones P.W.
      Occult anal sphincter injuries—myth or reality?.
      In that study of primiparous women, all women were examined by a trained fellow after the examination and grading of tear by the obstetrical care provider and confirmed by endoanal ultrasound prior to repair (considered the gold standard). When examined systematically as described above, all but 1.6% (3/182) of women were correctly diagnosed on exam; the other 3 had occult OASIS representing the false-negative rate of examination, 2 of which only affected the internal sphincter, and would have thus been undetectable on physical examination.
      When the diagnosis of OASIS is obtained from endoanal ultrasound evaluation within 2 months of delivery, the incidence of any degree of anal sphincter defect in primiparous women is reported to be as high as 27% to 35%, and between 4% and 8.5% of multiparous women have a new sphincter defect.
      • Sultan A.H.
      • Kamm M.A.
      • Hudson C.N.
      • Thomas J.M.
      • Bartram C.I.
      Anal-sphincter disruption during vaginal delivery.
      • Oberwalder M.
      • Connor J.
      • Wexner S.D.
      Meta-analysis to determine the incidence of obstetric anal sphincter damage.

      Risk Factors for OASIS

      Risk factors commonly associated with obstetric anal sphincter tears include maternal, delivery, and infant characteristics. Table 3 shows a summary of OR for various risks factors from studies reporting this information.
      • Handa V.L.
      • Danielsen B.H.
      • Gilbert W.M.
      Obstetric anal sphincter lacerations.
      • Zetterstrom J.
      • Lopez A.
      • Anzen B.
      • Norman M.
      • Holmstrom B.
      • Mellgren A.
      Anal sphincter tears at vaginal delivery: risk factors and clinical outcome of primary repair.
      • Richter H.E.
      • Brumfield C.G.
      • Cliver S.P.
      • Burgio K.L.
      • Neely C.L.
      • Varner R.E.
      Risk factors associated with anal sphincter tear: a comparison of primiparous patients, vaginal births after cesarean deliveries, and patients with previous vaginal delivery.
      • Richter H.E.
      • Fielding J.R.
      • Bradley C.S.
      • Handa V.L.
      • Fine P.
      • Fitzgerald M.P.
      • et al.
      Endoanal ultrasound findings and fecal incontinence symptoms in women with and without recognized anal sphincter tears.
      • Gerdin E.
      • Sverrisdottir G.
      • Badi A.
      • Carlsson B.
      • Graf W.
      The role of maternal age and episiotomy in the risk of anal sphincter tears during childbirth.
      • Baghestan E.
      • Irgens L.M.
      • Bordahl P.E.
      • Rasmussen S.
      Trends in risk factors for obstetric anal sphincter injuries in Norway.
      • Berggren V.
      • Gottvall K.
      • Isman E.
      • Bergstrom S.
      • Ekeus C.
      Infibulated women have an increased risk of anal sphincter tears at delivery:a population-based Swedish register study of 250000 births.
      • Fenner D.E.
      • Genberg B.
      • Brahma P.
      • Marek L.
      • DeLancey J.O.
      Fecal and urinary incontinence after vaginal delivery with anal sphincter disruption in an obstetrics unit in the United States.
      • McPherson K.C.
      • Beggs A.D.
      • Sultan A.H.
      • Thakar R.
      Can the risk of obstetric anal sphincter injuries (OASIS) be predicted using a risk-scoring system?.
      • Murphy D.J.
      • Macleod M.
      • Bahl R.
      • Strachan B.
      A cohort study of maternal and neonatal morbidity in relation to use of sequential instruments at operative vaginal delivery.
      • de Leeuw J.W.
      • de Wit C.
      • Kuijken J.P.
      • Bruinse H.W.
      Mediolateral episiotomy reduces the risk for anal sphincter injury during operative vaginal delivery.
      • Kudish B.
      • Blackwell S.
      • McNeeley S.G.
      • Bujold E.
      • Kruger M.
      • Hendrix S.L.
      • et al.
      Operative vaginal delivery and midline episiotomy: a bad combination for the perineum.
      • Dandolu V.
      • Chatwani A.
      • Harmanli O.
      • Floro C.
      • Gaughan J.P.
      • Hernandez E.
      Risk factors for obstetrical anal sphincter lacerations.
      • Risnen S.
      • Vehvilinen-Julkunen K.
      • Cartwright R.
      • Gissler M.
      • Heinonen S.
      A prior cesarean section and incidence of obstetric anal sphincter injury.
      • Boggs E.W.
      • Berger H.
      • Urquia M.
      • Mcdermott C.
      Mode of delivery following obstetric anal sphincter injury.
      • Rognant S.
      • Benoist G.
      • Creveuil C.
      • Dreyfus M.
      Obstetrical situations with a high risk of anal sphincter laceration in vacuum-assisted deliveries.
      • Wu J.M.
      • Williams K.S.
      • Hundley A.F.
      • Connolly A.
      • Visco A.G.
      • Stubbs T.
      Occiput posterior fetal head position increases the risk of anal sphincter injury in vacuum-assisted deliveries.
      Table 3Risks factors for OASIS
      Maternal risks factorsOR
      All OR 95% confidence intervals are significant, i.e. do not cross 1
      Primiparity
      • Handa V.L.
      • Danielsen B.H.
      • Gilbert W.M.
      Obstetric anal sphincter lacerations.
      • Zetterstrom J.
      • Lopez A.
      • Anzen B.
      • Norman M.
      • Holmstrom B.
      • Mellgren A.
      Anal sphincter tears at vaginal delivery: risk factors and clinical outcome of primary repair.
      • Richter H.E.
      • Brumfield C.G.
      • Cliver S.P.
      • Burgio K.L.
      • Neely C.L.
      • Varner R.E.
      Risk factors associated with anal sphincter tear: a comparison of primiparous patients, vaginal births after cesarean deliveries, and patients with previous vaginal delivery.
      • Richter H.E.
      • Fielding J.R.
      • Bradley C.S.
      • Handa V.L.
      • Fine P.
      • Fitzgerald M.P.
      • et al.
      Endoanal ultrasound findings and fecal incontinence symptoms in women with and without recognized anal sphincter tears.
      • Gerdin E.
      • Sverrisdottir G.
      • Badi A.
      • Carlsson B.
      • Graf W.
      The role of maternal age and episiotomy in the risk of anal sphincter tears during childbirth.
      • Baghestan E.
      • Irgens L.M.
      • Bordahl P.E.
      • Rasmussen S.
      Trends in risk factors for obstetric anal sphincter injuries in Norway.
      3.5 to 9.8
      Age (>35)
      • Baghestan E.
      • Irgens L.M.
      • Bordahl P.E.
      • Rasmussen S.
      Trends in risk factors for obstetric anal sphincter injuries in Norway.
      1.1
      Age (>27)
      • Gerdin E.
      • Sverrisdottir G.
      • Badi A.
      • Carlsson B.
      • Graf W.
      The role of maternal age and episiotomy in the risk of anal sphincter tears during childbirth.
      1.9
      Race
      • Handa V.L.
      • Danielsen B.H.
      • Gilbert W.M.
      Obstetric anal sphincter lacerations.
      • Gerdin E.
      • Sverrisdottir G.
      • Badi A.
      • Carlsson B.
      • Graf W.
      The role of maternal age and episiotomy in the risk of anal sphincter tears during childbirth.
      1.4 to 2.5
      Maternal diabetes
      • Handa V.L.
      • Danielsen B.H.
      • Gilbert W.M.
      Obstetric anal sphincter lacerations.
      • Gerdin E.
      • Sverrisdottir G.
      • Badi A.
      • Carlsson B.
      • Graf W.
      The role of maternal age and episiotomy in the risk of anal sphincter tears during childbirth.
      1.2 to 1.4
      Infibulation
      • Berggren V.
      • Gottvall K.
      • Isman E.
      • Bergstrom S.
      • Ekeus C.
      Infibulated women have an increased risk of anal sphincter tears at delivery:a population-based Swedish register study of 250000 births.
      1.8 to 2.7
      Delivery risks factorsOR
      Operative vaginal delivery
      Presence of episiotomy not dissociated from instrumental
       Vacuum
      • Handa V.L.
      • Danielsen B.H.
      • Gilbert W.M.
      Obstetric anal sphincter lacerations.
      • Richter H.E.
      • Brumfield C.G.
      • Cliver S.P.
      • Burgio K.L.
      • Neely C.L.
      • Varner R.E.
      Risk factors associated with anal sphincter tear: a comparison of primiparous patients, vaginal births after cesarean deliveries, and patients with previous vaginal delivery.
      • Baghestan E.
      • Irgens L.M.
      • Bordahl P.E.
      • Rasmussen S.
      Trends in risk factors for obstetric anal sphincter injuries in Norway.
      • Fenner D.E.
      • Genberg B.
      • Brahma P.
      • Marek L.
      • DeLancey J.O.
      Fecal and urinary incontinence after vaginal delivery with anal sphincter disruption in an obstetrics unit in the United States.
      1.5 to 3.5
       Forceps
      • Handa V.L.
      • Danielsen B.H.
      • Gilbert W.M.
      Obstetric anal sphincter lacerations.
      • Richter H.E.
      • Brumfield C.G.
      • Cliver S.P.
      • Burgio K.L.
      • Neely C.L.
      • Varner R.E.
      Risk factors associated with anal sphincter tear: a comparison of primiparous patients, vaginal births after cesarean deliveries, and patients with previous vaginal delivery.
      • Baghestan E.
      • Irgens L.M.
      • Bordahl P.E.
      • Rasmussen S.
      Trends in risk factors for obstetric anal sphincter injuries in Norway.
      • Fenner D.E.
      • Genberg B.
      • Brahma P.
      • Marek L.
      • DeLancey J.O.
      Fecal and urinary incontinence after vaginal delivery with anal sphincter disruption in an obstetrics unit in the United States.
      • McPherson K.C.
      • Beggs A.D.
      • Sultan A.H.
      • Thakar R.
      Can the risk of obstetric anal sphincter injuries (OASIS) be predicted using a risk-scoring system?.
      2.3 to 5.6
       Vacuum+forceps
      • Baghestan E.
      • Irgens L.M.
      • Bordahl P.E.
      • Rasmussen S.
      Trends in risk factors for obstetric anal sphincter injuries in Norway.
      • Murphy D.J.
      • Macleod M.
      • Bahl R.
      • Strachan B.
      A cohort study of maternal and neonatal morbidity in relation to use of sequential instruments at operative vaginal delivery.
      8.1
      Episiotomy
       Midline
      • Fenner D.E.
      • Genberg B.
      • Brahma P.
      • Marek L.
      • DeLancey J.O.
      Fecal and urinary incontinence after vaginal delivery with anal sphincter disruption in an obstetrics unit in the United States.
      2.3 to 5.5
       Mediolateral
      • Fenner D.E.
      • Genberg B.
      • Brahma P.
      • Marek L.
      • DeLancey J.O.
      Fecal and urinary incontinence after vaginal delivery with anal sphincter disruption in an obstetrics unit in the United States.
      • de Leeuw J.W.
      • de Wit C.
      • Kuijken J.P.
      • Bruinse H.W.
      Mediolateral episiotomy reduces the risk for anal sphincter injury during operative vaginal delivery.
      0.21
      Mediolat episiotomy+instrumental
      • de Leeuw J.W.
      • de Wit C.
      • Kuijken J.P.
      • Bruinse H.W.
      Mediolateral episiotomy reduces the risk for anal sphincter injury during operative vaginal delivery.
       Vacuum0.11
       Forceps0.08
      Midline episiotomy+instrumental (nulliparous)
      • Kudish B.
      • Blackwell S.
      • McNeeley S.G.
      • Bujold E.
      • Kruger M.
      • Hendrix S.L.
      • et al.
      Operative vaginal delivery and midline episiotomy: a bad combination for the perineum.
       Vacuum4.5
       Forceps8.6
      Unspecified episiotomy+instrumental
      • Dandolu V.
      • Chatwani A.
      • Harmanli O.
      • Floro C.
      • Gaughan J.P.
      • Hernandez E.
      Risk factors for obstetrical anal sphincter lacerations.
       Vacuum2.9
       Forceps3.9
      Epidural
      • Gerdin E.
      • Sverrisdottir G.
      • Badi A.
      • Carlsson B.
      • Graf W.
      The role of maternal age and episiotomy in the risk of anal sphincter tears during childbirth.
      1.1 to 2.2
      Second stage >1 h
      In primiparous
      1.5
      Shoulder dystocia2.7 to 3.3
      VBAC
      • Richter H.E.
      • Brumfield C.G.
      • Cliver S.P.
      • Burgio K.L.
      • Neely C.L.
      • Varner R.E.
      Risk factors associated with anal sphincter tear: a comparison of primiparous patients, vaginal births after cesarean deliveries, and patients with previous vaginal delivery.
      • Risnen S.
      • Vehvilinen-Julkunen K.
      • Cartwright R.
      • Gissler M.
      • Heinonen S.
      A prior cesarean section and incidence of obstetric anal sphincter injury.
      1.4 to 5.5
      Water birth
      • McPherson K.C.
      • Beggs A.D.
      • Sultan A.H.
      • Thakar R.
      Can the risk of obstetric anal sphincter injuries (OASIS) be predicted using a risk-scoring system?.
      1.46
      Oxytocin augmentation
      In primiparous
      • Boggs E.W.
      • Berger H.
      • Urquia M.
      • Mcdermott C.
      Mode of delivery following obstetric anal sphincter injury.
      1.2
      Infant risks factorsOR
      Birth weight>4000 gm
      • Zetterstrom J.
      • Lopez A.
      • Anzen B.
      • Norman M.
      • Holmstrom B.
      • Mellgren A.
      Anal sphincter tears at vaginal delivery: risk factors and clinical outcome of primary repair.
      2.2 to 3.0
      Malpresentation
      • Gerdin E.
      • Sverrisdottir G.
      • Badi A.
      • Carlsson B.
      • Graf W.
      The role of maternal age and episiotomy in the risk of anal sphincter tears during childbirth.
      2.0
      Postmaturity
      • Zetterstrom J.
      • Lopez A.
      • Anzen B.
      • Norman M.
      • Holmstrom B.
      • Mellgren A.
      Anal sphincter tears at vaginal delivery: risk factors and clinical outcome of primary repair.
      • Baghestan E.
      • Irgens L.M.
      • Bordahl P.E.
      • Rasmussen S.
      Trends in risk factors for obstetric anal sphincter injuries in Norway.
      1.1 to 2.5
      Fetal distress1.3
      OP
      Occiput posterior
       SVD
      • Gerdin E.
      • Sverrisdottir G.
      • Badi A.
      • Carlsson B.
      • Graf W.
      The role of maternal age and episiotomy in the risk of anal sphincter tears during childbirth.
      2.0
       Instrumental
      • Rognant S.
      • Benoist G.
      • Creveuil C.
      • Dreyfus M.
      Obstetrical situations with a high risk of anal sphincter laceration in vacuum-assisted deliveries.
      • Wu J.M.
      • Williams K.S.
      • Hundley A.F.
      • Connolly A.
      • Visco A.G.
      • Stubbs T.
      Occiput posterior fetal head position increases the risk of anal sphincter injury in vacuum-assisted deliveries.
      4.7
      VBAC: Vaginal birth after Caesarean
      * All OR 95% confidence intervals are significant, i.e. do not cross 1
      Presence of episiotomy not dissociated from instrumental
      In primiparous
      § Occiput posterior

      Maternal Risk Factors

      Maternal risk factors are presented in the first section of Table 3. Obesity is protective, in a dose-response manner (BMI 25 to <30: 0.89 [95% CI 0.85 to 0.95]; 30 to <35: 0.84 [95% CI 0.76 to 0.92]; and BMI>35: 0.70 [95% CI 0.59 to 0.82]).
      • Lindholm E.S.
      • Altman D.
      Risk of obstetric anal sphincter lacerations among obese women.

      Delivery Risk Factors

      Risks factors occurring at the time of delivery that may be independently associated with OASIS are included in the second section of Table 3. The impact of midline episiotomy and forceps, together or in isolation, are presented in Table 4.
      • Fitzgerald M.P.
      • Weber A.M.
      • Howden N.
      • Cundiff G.W.
      • Brown M.B.
      • Pelvic Floor Disorders Network
      Risk factors for anal sphincter tear during vaginal delivery.
      Table 4Risk of OASIS after instrumental delivery, with or without episiotomy (90% midline)
      CharacteristicNumber with factor in sphincter tear groupNumber with factor in vaginal control groupEstimated OR for factor being related to tear95% lower confidence limit for OR95% upper confidence limit for OR
      No vacuum, forceps, episiotomy or OP (reference group)912351.0
      Forceps1222513.67.923.2
      Fetal position OP52217.03.812.6
      Vacuum101386.34.010.1
      Prolonged second stage138665.63.68.6
      Episiotomy2201035.33.87.6
      Epidural3663363.21.66.2
      Forceps+episiotomy63625.310.262.6
      Prolonged second stage+forceps+episiotomy32324.46.986.5
      Epidural+forceps+episiotomy61441.013.5124.4
      Prolonged second stage+epidural+forceps+episiotomy32240.68.6191.8
      OP+forceps26321.66.275.6
      OP+vacuum1549.73.030.8
      OP+episiotomy33515.95.843.2
      OP+episiotomy+forceps18133.84.8239.5
      OP+episiotomy+epidural+forceps170
      OR: odds ratio; OP: occiput posterior

      Infant Risk Factors

      Specific infant characteristics appearing independently increase the risk of OASIS presented in the third section of Table 3.

      INTERVENTIONS TO PREVENT OASIS

      Risk factors for OASIS often become apparent late in labour, and the degree to which these factors can potentially be modified during labour is yet to be determined. However, some methods of performing the delivery may show evidence of protection.
      • Thakar R.
      • Eason E.
      Prevention of perineal trauma.

      Head Control

      Slowing down the delivery of the head and instructing women to not push at the delivery of the head, using thus only the uterine expulsive efforts, decreases the incidence of OASIS by 50% to 70%, as shown by multicentre studies in Norway.
      • Laine K.
      • Pirhonen T.
      • Rolland R.
      • Pirhonen J.
      Decreasing the incidence of anal sphincter tears during delivery.
      • Hals E.
      • Oian P.
      • Pirhonen T.
      • Gissler M.
      • Hjelle S.
      • Nilsen E.B.
      • et al.
      A multicenter interventional program to reduce the incidence of anal sphincter tears.

      Perineal Support

      The protective role of perineal support (whereby the delivery care provider holds the perineum with a sponge, applying medial pressure) in isolation is unclear. A Cochrane review including RCTs on the topic
      • Aasheim V.
      • Nilsen A.B.
      • Lukasse M.
      • Reinar L.M.
      Perineal techniques during the second stage of labour for reducing perineal trauma.
      failed to show a benefit; however, the results were heavily influenced by a large RCT of hands-poised versus hands-on techniques, which included both slowing the head and supporting the perineum. In the study, midwives assigned to poised hands were also allowed to slow the head (by applying pressure on the head itself to control its speed of expulsion) if delivering too fast, which effectively biased the results.
      A 2011 Cochrane review showed that the application of warm compresses to the perineum (OR 0.5) as well as intra-partum perineal massage (OR 0.5) both decrease the risk of OASIS.
      • Aasheim V.
      • Nilsen A.B.
      • Lukasse M.
      • Reinar L.M.
      Perineal techniques during the second stage of labour for reducing perineal trauma.
      • Stamp G.
      • Kruzins G.
      • Crowther C.
      Perineal massage in labour and prevention of perineal trauma: randomised controlled trial.
      Perineal massage is done with lubricant,using a gentle, slow massage, with 2 fingers of the [obstetrical care provider’s] gloved hand moving from side to side just inside the patient’s vagina. Mild, downward pressure (towards the rectum) is applied with steady, lateral strokes, which last 1 second in each direction.
      • Albers L.L.
      • Sedler K.D.
      • Bedrick E.J.
      • Teaf D.
      • Peralta P.
      Midwifery care measures in the second stage of labor and reduction of genital tract trauma at birth: a randomized trial.

      Delivery Position

      While kneeling versus sitting has no impact on rate of OASIS, a standing position (upright position without buttocks support: upright standing, squatting, kneeling) versus a sitting position (upright position but with support of the ischial tuberosities, with or without sacral support) might increase the risk of OASIS, as shown in a retrospective analysis of 814 women (650 standing, 264 sitting, any parity) in which women standing for their delivery had a nearly 7-fold increase in OASIS (2.5% vs. 0.38%).
      • Gareberg B.
      • Magnusson B.
      • Sultan B.
      • Wennerholm U.-B.
      • Wennergren M.
      • Hagberg H.
      Birth in standing position: a high frequency of third degree tears.
      A 2012 RCT comparing traditional method of delivery (no passive second stage, and active second stage in the dorsal lithotomy) versus “alternate” method of delivery (passive second stage lasting up to strong urge or 120 min, and active second stage in the lateral “Gasquet” position — with upper hip flexed, foot on stirrup higher than knee) showed no difference in rate of OASIS.
      • Walker C.
      • Rodriguez T.
      • Herranz A.
      • Espinosa J.A.
      • Sanchez E.
      • Espuna-Pons M.
      Alternative model of birth to reduce the risk of assisted vaginal delivery and perineal trauma.

      Episiotomy

      There is no doubt that restricted use of episiotomy, of any type, is preferable in women having a spontaneous vaginal delivery.
      • Carroli G.
      • Mignini L.
      Episiotomy for vaginal birth.
      The results of a pilot RCT of routine versus restrictive mediolateral episiotomy in nulliparous women, undergoing instrumental delivery did not reach statistical significance due to a small sample size.
      • Murphy D.J.
      • Macleod M.
      • Bahl R.
      • Goyder K.
      • Howarth L.
      • Strachan B.
      A randomised controlled trial of routine versus restrictive use of episiotomy at operative vaginal delivery: a multicentre pilot study.
      Most studies identify midline episiotomy as a risk factor,
      • Aytan H.
      • Tapisiz O.L.
      • Tuncay G.
      • Avsar F.A.
      Severe perineal lacerations in nulliparous women and episiotomy type.
      but some do not.
      • Handa V.L.
      • Danielsen B.H.
      • Gilbert W.M.
      Obstetric anal sphincter lacerations.
      This might be related to poor coding in those studies that assess the outcome based on database information.
      • Brubaker L.
      • Bradley C.S.
      • Handa V.L.
      • Richter H.E.
      • Visco A.
      • Brown M.B.
      • et al.
      Anal sphincter laceration at vaginal delivery: is this event coded accurately?.
      However, while the published rate of OASIS following mediolateral episiotomy varies between 0.5% to 7%, it may reach as high as 17% to 19% following a midline episiotomy.
      • Fenner D.E.
      • Genberg B.
      • Brahma P.
      • Marek L.
      • DeLancey J.O.
      Fecal and urinary incontinence after vaginal delivery with anal sphincter disruption in an obstetrics unit in the United States.
      • McPherson K.C.
      • Beggs A.D.
      • Sultan A.H.
      • Thakar R.
      Can the risk of obstetric anal sphincter injuries (OASIS) be predicted using a risk-scoring system?.
      • Murphy D.J.
      • Macleod M.
      • Bahl R.
      • Strachan B.
      A cohort study of maternal and neonatal morbidity in relation to use of sequential instruments at operative vaginal delivery.
      • de Leeuw J.W.
      • de Wit C.
      • Kuijken J.P.
      • Bruinse H.W.
      Mediolateral episiotomy reduces the risk for anal sphincter injury during operative vaginal delivery.
      • Kudish B.
      • Blackwell S.
      • McNeeley S.G.
      • Bujold E.
      • Kruger M.
      • Hendrix S.L.
      • et al.
      Operative vaginal delivery and midline episiotomy: a bad combination for the perineum.
      • Dandolu V.
      • Chatwani A.
      • Harmanli O.
      • Floro C.
      • Gaughan J.P.
      • Hernandez E.
      Risk factors for obstetrical anal sphincter lacerations.
      • Risnen S.
      • Vehvilinen-Julkunen K.
      • Cartwright R.
      • Gissler M.
      • Heinonen S.
      A prior cesarean section and incidence of obstetric anal sphincter injury.
      • Boggs E.W.
      • Berger H.
      • Urquia M.
      • Mcdermott C.
      Mode of delivery following obstetric anal sphincter injury.
      • Rognant S.
      • Benoist G.
      • Creveuil C.
      • Dreyfus M.
      Obstetrical situations with a high risk of anal sphincter laceration in vacuum-assisted deliveries.
      • Wu J.M.
      • Williams K.S.
      • Hundley A.F.
      • Connolly A.
      • Visco A.G.
      • Stubbs T.
      Occiput posterior fetal head position increases the risk of anal sphincter injury in vacuum-assisted deliveries.
      • Lindholm E.S.
      • Altman D.
      Risk of obstetric anal sphincter lacerations among obese women.
      • Fitzgerald M.P.
      • Weber A.M.
      • Howden N.
      • Cundiff G.W.
      • Brown M.B.
      • Pelvic Floor Disorders Network
      Risk factors for anal sphincter tear during vaginal delivery.
      • Thakar R.
      • Eason E.
      Prevention of perineal trauma.
      • Laine K.
      • Pirhonen T.
      • Rolland R.
      • Pirhonen J.
      Decreasing the incidence of anal sphincter tears during delivery.
      • Hals E.
      • Oian P.
      • Pirhonen T.
      • Gissler M.
      • Hjelle S.
      • Nilsen E.B.
      • et al.
      A multicenter interventional program to reduce the incidence of anal sphincter tears.
      • Aasheim V.
      • Nilsen A.B.
      • Lukasse M.
      • Reinar L.M.
      Perineal techniques during the second stage of labour for reducing perineal trauma.
      • Stamp G.
      • Kruzins G.
      • Crowther C.
      Perineal massage in labour and prevention of perineal trauma: randomised controlled trial.
      • Albers L.L.
      • Sedler K.D.
      • Bedrick E.J.
      • Teaf D.
      • Peralta P.
      Midwifery care measures in the second stage of labor and reduction of genital tract trauma at birth: a randomized trial.
      • Gareberg B.
      • Magnusson B.
      • Sultan B.
      • Wennerholm U.-B.
      • Wennergren M.
      • Hagberg H.
      Birth in standing position: a high frequency of third degree tears.
      • Walker C.
      • Rodriguez T.
      • Herranz A.
      • Espinosa J.A.
      • Sanchez E.
      • Espuna-Pons M.
      Alternative model of birth to reduce the risk of assisted vaginal delivery and perineal trauma.
      • Carroli G.
      • Mignini L.
      Episiotomy for vaginal birth.
      • Murphy D.J.
      • Macleod M.
      • Bahl R.
      • Goyder K.
      • Howarth L.
      • Strachan B.
      A randomised controlled trial of routine versus restrictive use of episiotomy at operative vaginal delivery: a multicentre pilot study.
      • Aytan H.
      • Tapisiz O.L.
      • Tuncay G.
      • Avsar F.A.
      Severe perineal lacerations in nulliparous women and episiotomy type.
      • Brubaker L.
      • Bradley C.S.
      • Handa V.L.
      • Richter H.E.
      • Visco A.
      • Brown M.B.
      • et al.
      Anal sphincter laceration at vaginal delivery: is this event coded accurately?.
      • Fernando R.J.
      • Sultan A.H.
      • Kettle C.
      • Thakar R.
      Methods of repair for obstetric anal sphincter injury.
      In those having an operative vaginal delivery, a retrospective large Dutch database study suggested that a mediolateral or lateral episiotomy lead to less anal sphincter injuries than no episiotomy or a midline episiotomy.
      • de Leeuw J.W.
      • de Wit C.
      • Kuijken J.P.
      • Bruinse H.W.
      Mediolateral episiotomy reduces the risk for anal sphincter injury during operative vaginal delivery.
      The impact of mediolateral episiotomy is somewhat controversial in instrumental deliveries in primiparous women. Some authors report an independent increased risk of OASIS if a mediolateral episiotomy is performed during instrumented birth (OR 4.04);
      • Andrews V.
      • Sultan A.H.
      • Thakar R.
      • Jones P.W.
      Risk factors for obstetric anal sphincter injury: a prospective study.
      however, once adjusted for instrumental delivery, the type of episiotomy no longer remained a risk factor. Others report a lower rates of OASIS
      • de Leeuw J.W.
      • Struijk P.C.
      • Vierhout M.E.
      • Wallenburg H.C.S.
      Risk factors for third degree perineal ruptures during delivery.
      • Raisanen S.H.
      • Vehvilainen-Julkunen K.
      • Gissler M.
      • Heinonen S.
      Lateral episiotomy protects primiparous but not multiparous women from obstetric anal sphincter rupture.
      • Revicky V.
      • Nirmal D.
      • Mukhopadhyay S.
      • Morris E.P.
      • Nieto J.J.
      Could a mediolateral episiotomy prevent obstetric anal sphincter injury?.
      and severe perineal trauma (high vaginal sulcus and OASIS combined)
      • Carroli G.
      • Mignini L.
      Episiotomy for vaginal birth.
      with mediolateral episiotomy than with no episiotomy (OR 0.2 to 0.8). The balance of the evidence suggests that a mediolateral episiotomy likely does not increase the risk of OASIS at the time of instrumental delivery of a primiparous woman, and in fact, may decrease the incidence of OASIS compared with no episiotomy.
      There is only one published RCT (published in 1980) comparing rates of OASIS between midline and mediolateral episiotomy in nulliparas.
      • Coats P.M.
      • Chan K.K.
      • Wilkins M.
      • Beard R.J.
      A comparison between midline and mediolateral episiotomies.
      In that study, 12% of women who had a midline episiotomy sustained an OASIS, versus 2% of those who had a mediolateral. This study had significant limitations including a number of protocol violations. For example, if an obstetrical care provider was opposed to midline incisions, a mediolateral episiotomy was performed instead and the patient excluded from the analysis. In a prospective cohort study of 1302 women who delivered vaginally, and who all received an episiotomy, 426 received midline and 876 mediolateral episiotomy, according to the practitioner’s preferences.
      • Sooklim R.
      • Thinkhamrop J.
      • Lumbiganon P.
      • Prasertcharoensuk W.
      • Pattamadilok J.
      • Seekorn K.
      • et al.
      The outcomes of midline versus medio-lateral episiotomy.
      Deep perineal tears (which included but were not limited to OASIS) were present in 14.8% of those who had a midline episiotomy versus 7% of those who had a mediolateral episiotomy.
      The terminology used in the literature is at times unclear between midline, mediolateral, and lateral episiotomies. A standardization has been proposed
      • Kalis V.
      • Laine K.
      • de Leeuw J.W.
      • Ismail K.M.
      • Tincello D.G.
      Classification of episiotomy: towards a standardisation of terminology.
      (as shown in Figure 2; for a more detailed illustration, see online eFigure 2). A midline episiotomy (line #1) should indicate those starting in the midline and continuing at a 0° angle from the vertical; mediolateral (line #4) episiotomies should represent those done starting in the midline but at an angle greater than 0° from the vertical line; while a lateral (#5) episiotomy starts off the midline and is carried at an angle greater than 0° from the vertical. Other incisions shown include: modified median (inverted “T” incision, #2), “J”-shaped episiotomy (#3), and the seldom used radical lateral (Schuchardt incision, #6).
      • Stedenfeldt M.
      • Pirhonen J.
      • Blix E.
      • Wilsgaard T.
      • Vonen B.
      • Oian P.
      Episiotomy characteristics and risks for obstetric anal sphincter injuries: a case-control study.
      The angle of the episiotomy affects the occurrence of OASIS. A more acute (vertical) angle appears to increase the risk of OASIS; in an RCT comparing mediolateral episiotomies made at 60° and 40° angles from the vertical, the risk of OASIS was 2.4% versus 5.5%, respectively (did not reach statistical significance); however, 60° episiotomies carried higher short-term pain.
      • El Din A.S.S.
      • Kamal M.M.
      • Amin M.A.
      Comparison between two incision angles of mediolateral episiotomy in primiparous women: a randomized controlled trial.
      This likely reflects how far away from the anal sphincter complex the incision is.
      The impact of the starting point of the episiotomy (mediolateral vs. lateral) appears less important. In a large RCT, published only in abstract form in 2014, comparing mediolateral to lateral episiotomies.
      • Karbanova J.
      • Rusavy Z.
      • Betincova L.
      • Jansova M.
      • Parizek A.
      • Kalis V.
      Clinical evaluation of peripartum outcomes of mediolateral versus lateral episiotomy.
      In this trial of 790 women, the incidence of OASIS did not differ between a mediolateral (60° off the midline) and a lateral incision (1 to 2 cm laterally from the midline, angled towards the ischial tuberosity): 1.5% versus 1.3%, respectively. There also seem to have no impact on postpartum pain or sexually between mediolateral and lateral.
      • Fodstad K.
      • Staff A.C.
      • Laine K.
      Effect of different episiotomy techniques on perineal pain and sexual activity 3 months after delivery.
      Looking at healed episiotomy scars, the risk of sustaining an OASIS is decreased when
      • Stedenfeldt M.
      • Pirhonen J.
      • Blix E.
      • Wilsgaard T.
      • Vonen B.
      • Oian P.
      Episiotomy characteristics and risks for obstetric anal sphincter injuries: a case-control study.
      :
      • the tip of the episiotomy is further away from a vertical line drawn from the vagina to anus: OR 0.30 for each 5.5 mm increase in the distance between the midline vertical line and the tip of the episiotomy,
      • a lateral incision is done: OR 0.44 for each 4.5 mm distance increase off the midline for the incision start (i.e. less OASIS when the incision started off the
      • 6 o’clock location on the introitus, e.g. 4 o’clock),
      • a longer episiotomy was done: OR 0.25 for each increase of 5.5 mm in episiotomy length, and/or
      • the healed angle is between 15° and 60°.
      In another study, primigravidas who had mediolateral episiotomies and OASIS had, when examined 3 months postpartum, a mean healed angle of 30°, compared with 38° in those without OASIS.
      • Eogan M.
      • Daly L.
      • O’Connell P.R.
      • O’Herlihy C.
      Does the angle of episiotomy affect the incidence of anal sphincter injury?.
      However, it was shown that there is a 20° difference between the incision angle of an episiotomy (typically performed when the head is crowning) and the sutured angle once healed: whereas the incision angle was 40° from midline, the angle measured once healed and scarred was 20°.
      • Kalis V.
      • Karbanova J.
      • Horak M.
      • Lobovsky L.
      • Kralickova M.
      • Rokyta Z.
      The incision angle of mediolateral episiotomy before delivery and after repair.
      In other words, to obtain a healed angle of 30°, one must incise at a 50° angle.

      Instrumental Delivery

      If instrumental delivery is indicated, vacuum extraction carries less risk to the anal sphincter than forceps.
      • Hirsch E.
      • Haney E.I.
      • Gordon T.E.
      • Silver R.K.
      Reducing high-order perineal laceration during operative vaginal delivery.
      • O’Mahony F.
      • Hofmeyr G.J.
      • Menon V.
      Choice of instruments for assisted vaginal delivery.
      Most data support the use of mediolateral episiotomy to protect against OASIS in primiparous women having instrumental delivery over no episiotomy.
      • de Leeuw J.W.
      • de Wit C.
      • Kuijken J.P.
      • Bruinse H.W.
      Mediolateral episiotomy reduces the risk for anal sphincter injury during operative vaginal delivery.
      • Raisanen S.H.
      • Vehvilainen-Julkunen K.
      • Gissler M.
      • Heinonen S.
      Lateral episiotomy protects primiparous but not multiparous women from obstetric anal sphincter rupture.
      • Macleod M.
      • Strachan B.
      • Bahl R.
      • Howarth L.
      • Goyder K.
      • Van de Venne M.
      • et al.
      A prospective cohort study of maternal and neonatal morbidity in relation to use of episiotomy at operative vaginal delivery.
      • Jango H.
      • Langhoff-Roos J.
      • Rosthoj S.
      • Sakse A.
      Modifiable risk factors of obstetric anal sphincter injury in primiparous women: a population-based cohort study.
      When a midline episiotomy is performed concurrently with an operative vaginal delivery, it acts synergistically in increasing OASIS.
      • Kudish B.
      • Blackwell S.
      • McNeeley S.G.
      • Bujold E.
      • Kruger M.
      • Hendrix S.L.
      • et al.
      Operative vaginal delivery and midline episiotomy: a bad combination for the perineum.
      • Steed H.H.
      • Corbett T.C.
      • Mayes D.C.
      The value of routine episiotomy in forceps deliveries.
      It is possible that early removal of forceps (after delivery is assured, but before the largest diameter of the head is expelled) may also assist in limiting OASIS in forceps and vacuum deliveries, when combined with other practices such as rotating an occiput posterior baby to an occiput anterior position, selecting a vacuum instead of a forceps, performing a mediolateral episiotomy rather than a midline (only if an episiotomy is deemed necessary), and using minimal necessary maternal expulsive efforts at time of expulsion.
      • Hirsch E.
      • Haney E.I.
      • Gordon T.E.
      • Silver R.K.
      Reducing high-order perineal laceration during operative vaginal delivery.
      Some have raised the point of informed consent at the time of instrumental delivery, arguing that disclosure of the OASIS risk should be included, as well as the risks and benefits of any alternative such as Caesarean section.
      • Farrell S.A.
      Cesarean section versus forceps-assisted vaginal birth: it’s time to include pelvic injury in the risk-benefit equation.
      Clearly, performing a Caesarean would prevent OASIS, but performing it late in labour may not fully protect the anal canal, as nerve injury can still occur.
      • Donnelly V.
      • Fynes M.
      • Campbell D.
      • Johnson H.
      • O’Connell P.R.
      • O’Herlihy C.
      Obstetric events leading to anal sphincter damage.
      • Fynes M.
      • Donnelly V.S.
      • O’Connell P.R.
      • O’Herlihy C.
      Cesarean delivery and anal sphincter injury.

      Other

      Studies evaluating antepartum perineal massage,
      • Beckmann M.M.
      • Garrett A.J.
      Antenatal perineal massage for reducing perineal trauma.
      pushing position (kneeling vs. sitting),
      • Altman D.
      • Ragnar I.
      • Ekstrom A.
      • Tyden T.
      • Olsson S.E.
      Anal sphincter lacerations and upright delivery postures—a risk analysis from a randomized controlled trial.
      open versus closed glottis pushing,
      • Yildirim G.
      • Beji N.K.
      Effects of pushing techniques in birth on mother and fetus: a randomized study.
      Ritgen’s manoeuvre,
      • Jonsson E.R.
      • Elfaghi I.
      • Rydhstrom H.
      • Herbst A.
      Modified Ritgen’s maneuver for anal sphincter injury at delivery: a randomized controlled trial.
      water birth,
      • Cluett E.R.
      • Burns E.
      Immersion in water in labour and birth.
      and delayed pushing (in women with epidural)
      • Fitzpatrick M.
      A randomised clinical trial comparing the effects of delayed versus immediate pushing with epidural analgesia on mode of delivery and faecal continence.
      failed to show evidence of a protective effect on the anal canal.

      Summary Statement

      • 2.
        Obstetrical anal sphincter injuries are more commonly associated with forceps deliveries than with vacuum-assisted vaginal deliveries. (II-2)

      Recommendations

      • 3.
        In women having a spontaneous vaginal delivery, the rate of obstetrical anal sphincter injury is decreased when the obstetrical care provider slows the fetal head at crowning. (II-2A)
      • 4.
        Episiotomy:
        • a.
          At the time of either a spontaneous vaginal or instrumental delivery, the obstetrical care provider should follow a policy of “restricted” episiotomy (i.e. only if indicated), rather than “liberal” use (i.e. routine), for the prevention of obstetrical anal sphincter injury. (I-A)
        • b.
          If an episiotomy is deemed indicated, preference for a mediolateral over a midline should be considered. (II-2B) The optimal cutting angle appears to be no less than 45 degrees, ideally around 60 degrees. (II-2B)

      PRINCIPLES AND TYPES OF REPAIRS

      Obstetric anal sphincter injuries should be repaired by appropriately trained clinicians comfortable with such repairs. Repairs are typically carried out in the delivery room or the operating room. The operating room offers the benefits of access to optimal lighting, appropriate equipment, and aseptic conditions.
      • Sultan A.H.
      • Thakar R.
      Third and fourth degree tears.
      Additional equipment may be required for anal sphincter repairs including self-retaining retractors and Allis clamps. There have been no studies that have evaluated anaesthetics used in the repair of obstetric anal sphincter injuries. Although commonly repaired under local anaesthetic, general or regional anaesthesia maybe optimal as they provide both analgesia and muscle relaxation.
      • Sultan A.H.
      • Thakar R.
      Third and fourth degree tears.
      The EAS has inherent tone and when torn does retract within its capsular sheath. With muscle relaxation, the extent of the tear can be thoroughly evaluated and the sphincter ends can be identified, grasped, and repaired by either the end-to-end or the overlap technique. Local anaesthetic may be sufficient when only the superficial fibres of the EAS are disrupted,
      • Sultan A.H.
      • Thakar R.
      Lower genital tract and anal sphincter trauma.
      although without good analgesia, it may be difficult to make a proper diagnosis. In the United Kingdom, experts recommend completing the repair under general or epidural anaesthesia.
      • Royal College of Obstetricians and Gynaecologists
      The SOGC Urogynaecology Committee does not feel this is always necessary, as long as adequate analgesia is provided, either using local infiltration or pudendal nerve block.

      Suture Material

      Although the type of suture material used in the repair of obstetric anal sphincter tears may be important, there has been very little research carried out comparing different suture types used for sphincter repairs. Both absorbable and delayed absorbable sutures are commonly used. Although some colorectal surgeons use non-absorbable sutures for secondary repairs of anal sphincters, there is concern that such sutures may result in stitch abscesses or suture ends may cause discomfort requiring their removal.
      • Duggal N.
      • Mercado C.
      • Daniels K.
      • Bujor A.
      • Caughey A.B.
      • El Sayed Y.Y.
      Antibiotic prophylaxis for prevention of postpartum perineal wound complications: a randomized controlled trial.
      The suture ends should be cut short and the knots covered by the overlying superficial perineal muscles in order to minimize any discomfort from suture ends and knots. Monofilament sutures maybe beneficial as they are less likely to harbour organisms and predispose to infection.
      • Sultan A.H.
      • Thakar R.
      Lower genital tract and anal sphincter trauma.
      A randomized trial by Williams et al.
      • Williams A.
      • Adams E.J.
      • Tincello D.G.
      • Alfirevic Z.
      • Walkinshaw S.A.
      • Richmond D.H.
      How to repair an anal sphincter injury after vaginal delivery: results of a randomised controlled trial.
      (n=112), compared OASIS repairs with polyglactin (Vicryl) and polydioxanone (PDS). At 6 weeks, there was no significant difference in suture-related morbidity. There may be benefit to delayed absorbable suture with respect to longer term functional outcomes but this has yet to be evaluated in clinical trials. Many of the more recently published studies have used delayed absorbable sutures but have not been undertaken to compare suture material. Randomized trials with longer term outcomes including anal incontinence are required to compare suture materials.

      Repair of the Anal Mucosa

      Following a fourth degree perineal tear, the anal mucosa can be approximated by a number of techniques.
      • Sultan A.H.
      • Thakar R.
      Lower genital tract and anal sphincter trauma.
      The mucosal repair can be carried out with an interrupted 3-0 Vicryl suture with the knots tied in the anal lumen or external to the anal canal. Alternatively the anal mucosa can be approximated with a 3-0 PDS suture with a submucosal continuous suture. There are currently no studies that suggest a benefit from any of these repair techniques for the anal mucosa with respect to outcomes including anovaginal and rectovaginal fistulas. However figure-of-eight sutures should not be used as they can cause ischemia and poor healing of the anorectal mucosa.

      Separate Repair of the IAS

      The literature related to the techniques of repairing the anal sphincter following obstetric trauma has primarily focused on the repair of the external anal sphincter. However, the muscles involved in maintaining anal continence include not only the EAS but also the internal anal sphincter.
      The internal sphincter is a 3 to 5 mm thick continuation of the rectal smooth muscle and is under autonomic control. The IAS is responsible for maintaining continence at rest, by contributing to 70% to 85% of the resting anal pressure, and, to a lesser degree, of the anal pressure in response to sudden and constant rectal distension (40% and 65%, respectively).
      • Koelbl H.
      • Nitti V.
      • Baessler K.
      • Salvatore S.
      • Sultan A.
      • Yamaguchi O.
      Pathophysiology of urinary incontinence, faecal incontinence and pelvic organ prolapse.
      In response to rectal distension by feces, liquids, or gases, the pressures in the IAS drop to allow “sampling” (whereby the rectal content transiently enters in contact with sensory nerve ending of the anal canal to determine the bowel content (liquid, gas, or solid) and allow processing and decision about appropriateness of evacuation), associated with a reflex recto-anal contractile reflex if time is inconvenient.
      • Lunniss J.
      • Scott S.
      Pathophysiology of anal incontinence.
      Damage to the IAS muscle may lead to a poor seal and an impaired sampling reflex,
      • Koelbl H.
      • Nitti V.
      • Baessler K.
      • Salvatore S.
      • Sultan A.
      • Yamaguchi O.
      Pathophysiology of urinary incontinence, faecal incontinence and pelvic organ prolapse.
      leading to passive incontinence.
      Sultan and Thakar
      • Sultan A.H.
      • Thakar R.
      Lower genital tract and anal sphincter trauma.
      described identifying and approximating the IAS with interrupted sutures in addition to the overlap repair of the EAS. It can be difficult to identify the IAS which lies between the EAS and the anal mucosa. In comparison to the striated muscle of the EAS, the IAS is thin with a pale pink appearance in close proximity to the anal mucosa. It may appear similar to a “fascial” layer. A small prospective study, with historical controls, published by Lindqvist and Jernetz in 2010,
      • Lindqvist P.G.
      • Jernetz M.
      A modified surgical approach to women with obstetric anal sphincter tears by separate suturing of external and internal anal sphincter. A modified approach to obstetric anal sphincter injury.
      suggested that identifying and separately suturing the IAS may improve anal continence at 1 year. Both previously mentioned studies approximated the IAS in an “end-to-end” fashion using delayed absorbable sutures. In a randomized trial of obstetric sphincter repairs,
      • Fitzpatrick M.
      • Behan M.
      • O'Connell P.R.
      • O'Herlihy C.
      A randomized clinical trial comparing primary overlap with approximation repair of third-degree obstetric tears.
      9 women had sphincter tears that included the IAS and were independently approximated. In all 9 women the IAS was intact on follow-up endoanal ultrasound.
      Studies looking at functional results following OASIS repair report that more women with an IAS defect on endoanal ultrasound 6 months postpartum have anal incontinence, and those with incontinence report worse degree of symptoms than those without IAS.
      • Richter H.E.
      • Fielding J.R.
      • Bradley C.S.
      • Handa V.L.
      • Fine P.
      • Fitzgerald M.P.
      • et al.
      Endoanal ultrasound findings and fecal incontinence symptoms in women with and without recognized anal sphincter tears.
      • O’Mahony F.
      • Hofmeyr G.J.
      • Menon V.
      Choice of instruments for assisted vaginal delivery.
      • Nichols C.M.
      • Nam M.
      • Ramakrishnan V.
      • Lamb E.H.
      • Currie N.
      Anal sphincter defects and bowel symptoms in women with and without recognized anal sphincter trauma.
      • Nichols C.M.
      • Lamb E.H.
      • Ramakrishnan V.
      Differences in outcomes after third- versus fourth-degree perineal laceration repair: a prospective study.

      EAS Repair Techniques

      When repairing a torn anal sphincter following vaginal delivery the external anal sphincter can be approximated by 1 of 2 repair techniques; end-to-end repair or overlap repair. The torn ends of the EAS, normally under tonic contraction, tend to retract within their sheaths and can be found latero-posteriorly to the tear, often by palpation of a depression downward rather than lateral. The muscle ends must be identified and grasped with Allis clamps.
      With an end-to-end repair (for a detailed illustration, see online eFigure 3), the EAS ends may need to be mobilized using Metzenbaum scissors for the dissection. The muscle ends are then approximated end-to-end with 2 or 3 mattress sutures. In theory, mattress sutures may cause less tissue necrosis although there is no evidence to support one technique over the other. Sutures should include the fascial sheath.
      • Sultan A.H.
      • Thakar R.
      Third and fourth degree tears.
      With an overlap repair (for a detailed illustration, see online eFigure 3), the torn EAS muscle ends often needs much more dissection and mobilization.
      • Sultan A.H.
      • Thakar R.
      Third and fourth degree tears.
      The dissection is carried out using the ischioanal fat laterally as a landmark. The full lengths of the torn ends of the EAS (including fascial sheath) are overlapped in a double-breasted fashion.
      • Duggal N.
      • Mercado C.
      • Daniels K.
      • Bujor A.
      • Caughey A.B.
      • El Sayed Y.Y.
      Antibiotic prophylaxis for prevention of postpartum perineal wound complications: a randomized controlled trial.
      This type of repair is only possible with 3b or greater OASIS.
      • Fernando R.J.
      • Sultan A.H.
      • Kettle C.
      • Thakar R.
      Methods of repair for obstetric anal sphincter injury.
      Following the anal sphincter repair, which approximates the disrupted anal sphincter complex, the perineal body is reconstructed by suturing the perineal muscles. This takes tension off and provides support for the underlying muscle repair. The vaginal mucosa and perineal skin are repaired in the usual fashion. A rectovaginal exam at the completion of the repair is carried out to confirm the adequacy of the repair.
      If an obstetrical care provider is insufficiently experienced in the repair of third and fourth degree tear and an experienced obstetrical care provider is not available immediately or locally, repair can be delayed for 8 to 12 hours with no impact on anal incontinence and pelvic floor symptoms.
      • Nordenstam J.
      • Mellgren A.
      • Altman D.
      • Lopez A.
      • Johansson C.
      • Anzen B.
      • et al.
      Immediate or delayed repair of obstetric anal sphincter tears— a randomised controlled trial.

      Summary Statement

      • 3.
        Obstetrical anal sphincter injuries (OASIS) repair:
        • a.
          Suture-related morbidity is similar at 6 weeks following the use of either polyglactin 2-0 or polydioxanone 3-0 following repair. (I)
        • b.
          Repair of the internal anal sphincter is recommended as women who demonstrate an internal anal sphincter defect on postpartum ultrasound have more anal incontinence. (III)
        • c.
          Repair of the external anal sphincter should include the fascial sheath. An overlapping technique often requires more dissection and mobilization of the sphincter ends and is only possible with full thickness 3b sphincter tears or greater. (III)
        • d.
          A persistent defect of the external anal sphincter remote from delivery may increase the risk of worsening symptoms following subsequent vaginal deliveries. (II-2)

      Recommendation

      • 5.
        Repair can be delayed for 8 to 12 hours with no detrimental effect. Delay may be required so a more experienced care provider is available for the repair. (I-A)

      Comparison of Repair Techniques

      Historically, the most popular technique for the primary repair of obstetrical anal sphincter injuries has been the end-to-end approximation of the external anal sphincter with interrupted or figure-of-eight sutures. In contrast, the technique commonly used by colorectal surgeons to repair anal sphincter tears remote from delivery or unrelated to delivery is the overlap technique. The overlap technique, described by Parks and McPartlin
      • Parks A.G.
      • McPartlin J.F.
      Late repair of injuries of the anal sphincter.
      for the secondary repair of anal sphincters, was first evaluated for the primary repair of obstetric anal sphincter tears by Sultan et al. in his 1999 seminal study.
      • Sultan A.H.
      • Monga A.K.
      • Kumar D.
      • Stanton S.L.
      Primary repair of obstetric anal sphincter rupture using the overlap technique.
      The small study (n=27) showed that in comparison to matched historical controls with end-to-end repairs, overlap repairs resulted in less anal incontinence (8% vs. 41%).
      • Sultan A.H.
      • Kamm M.A.
      • Hudson C.N.
      • Bartram C.I.
      Third degree obstetric anal sphincter tears: risk factors and outcome of primary repair.
      Following this study several randomized trials have been published comparing end-to-end approximation and overlap repair of the EAS.
      A 2013 Cochrane review compared the effectiveness of these 2 immediate primary repair techniques in reducing subsequent anal incontinence, perineal pain, dyspareunia and improving quality of life.
      • Fernando R.J.
      • Sultan A.H.
      • Kettle C.
      • Thakar R.
      Methods of repair for obstetric anal sphincter injury.
      The authors included 6 trials involving 588 women.
      • Williams A.
      • Adams E.J.
      • Tincello D.G.
      • Alfirevic Z.
      • Walkinshaw S.A.
      • Richmond D.H.
      How to repair an anal sphincter injury after vaginal delivery: results of a randomised controlled trial.
      • Fitzpatrick M.
      • Behan M.
      • O'Connell P.R.
      • O'Herlihy C.
      A randomized clinical trial comparing primary overlap with approximation repair of third-degree obstetric tears.
      • Fernando R.J.
      • Sultan A.H.
      • Kettle C.
      • Radley S.
      • Jones P.
      • O'Brien P.M.S.
      Repair techniques for obstetric anal sphincter injuries: a randomized controlled trial.
      Three trials followed women for 12 months.
      • Fernando R.J.
      • Sultan A.H.
      • Kettle C.
      • Radley S.
      • Jones P.
      • O'Brien P.M.S.
      Repair techniques for obstetric anal sphincter injuries: a randomized controlled trial.
      The only outcomes showing a difference was for fecal urgency and fecal incontinence score, in favour of the overlapping repair from one trial with 52 women followed up at 12 months.
      • Fernando R.J.
      • Sultan A.H.
      • Kettle C.
      • Radley S.
      • Jones P.
      • O'Brien P.M.S.
      Repair techniques for obstetric anal sphincter injuries: a randomized controlled trial.
      An overlap repair resulted in fewer with deterioration of incontinence from 6 weeks to 12 months later (n=41).
      • Fernando R.J.
      • Sultan A.H.
      • Kettle C.
      • Radley S.
      • Jones P.
      • O'Brien P.M.S.
      Repair techniques for obstetric anal sphincter injuries: a randomized controlled trial.
      Another trial showed that at 36 months, these differences were no longer present.
      • Farrell S.A.
      • Flowerdew G.
      • Gilmour D.
      • Turnbull G.K.
      • Schmidt M.H.
      • Baskett T.F.
      • et al.
      Overlapping compared with end-to-end repair of complete third-degree or fourth-degree obstetric tears: three-year follow-up of a randomized controlled trial.
      However, the data are limited given the heterogeneity in the outcome measures, time points, and reported results. These studies included primiparous and parous women and partial and complete third degree tears. Furthermore, their surgical experience is not evaluated in the included studies. Consequently, the current literature does not support recommending one obstetric anal sphincter repair technique over the other.

      POSTOPERATIVE MANAGEMENT

      Prophylactic Antibiotics

      Only one randomized trial compared the effect of a single IV dose of a second generation cephalosporin (cefotetan or cefoxitin) on postpartum perineal wound complications (purulent discharge, or abscess and breakdown of repair) 2 weeks following third and fourth degree tears.
      • Duggal N.
      • Mercado C.
      • Daniels K.
      • Bujor A.
      • Caughey A.B.
      • El Sayed Y.Y.
      Antibiotic prophylaxis for prevention of postpartum perineal wound complications: a randomized controlled trial.
      Prophylactic antibiotics given at the time of obstetrical anal sphincter repair decreases maternal morbidity related to perineal wound complications: 8.2% of women who received antibiotics and 24.1% of women who received placebo suffered a wound complication (P<0.05), with a relative risk of 0.34 (95% CI 0.12 to 0.96).
      • Buppasiri P.
      • Lumbiganon P.
      • Thinkhamrop J.
      • Thinkhamrop B.
      Antibiotic prophylaxis for third- and fourth-degree perineal tear during vaginal birth.
      • Fernando R.
      • Sultan A.H.
      • Kettle C.
      • Thakar R.
      • Radley S.
      Methods of repair for obstetric anal sphincter injury.
      This Cochrane review reported that the study was limited by a high (27.2%) proportion of lack of follow-up. There are currently no studies that have evaluated the value of additional doses of antibiotics following repair of third and fourth degree perineal tears.

      Recommendation

      • 6.
        Prophylactic single dose intravenous antibiotics (2nd generation cephalosporin, e.g., cefotetan or cefoxitin) should be administered for the reduction of perineal wound complications following the repair of obstetrical anal sphincter injury. (I-A)

      Postoperative Bowel Regimen

      Postoperative bowel regimens following the primary repair of OASIS vary. Some regimens consist of laxatives and bulking agents to avoid constipation and any potential disruption of the repair from the passage of hard stool. Other regimens consist of bowel confinement techniques with the concern that bowel motions in the immediate postoperative period may threaten the integrity of the repair.
      Mahony et al.
      • Mahony R.
      • Behan M.
      • O'Herlihy C.
      • O'Connell P.R.
      Randomized, clinical trial of bowel confinement vs. laxative use after primary repair of a third-degree obstetric anal sphincter tear.
      performed a randomized trial to compare a laxative regiment (lactulose) with a constipating regiment (codeine phosphate) in the 3 days following repair of primary OASIS in 105 women. Laxative use was associated with a significantly earlier and less painful first bowel motion and an earlier hospital discharge postpartum. Troublesome constipation was noted in 19% of women receiving the constipating regimen compared to 5% receiving the laxative regimen. Two patients that received the constipating regimen required hospital admission for fecal impaction. Overall there were no significant differences in continence scores or anal manometry and endoanal scan findings between the groups at 3 months postpartum.
      In 2007 Eogan et al.
      • Eogan M.
      • Daly L.
      • Behan M.
      • O'Connell P.R.
      • O'Herlihy C.
      Randomised clinical trial of a laxative alone versus a laxative and a bulking agent after primary repair of obstetric anal sphincter injury.
      randomized (n=147) women to receive laxatives alone (lactulose) or laxatives and a bulking agent (lactulose and ispaghula husk, Fybogel) for 10 days after the repair of OASIS. Incontinence in the immediate postnatal period was more frequent in women taking the 2 preparations than in those taking lactulose alone (33% vs. 18%). There were no significant differences between the groups with respect to time to first bowel motion, length of hospital stay, or overall satisfaction related to bowel habits, and no significant difference in functional outcomes at 3 months.

      Recommendation

      • 7.
        Laxatives (e.g., lactulose) should be prescribed following the primary repair of obstetrical anal sphincter injury as they are associated with earlier and less painful first bowel motions and earlier discharge from hospital. Constipating agents and bulking agents are not recommended (I-A).

      Postoperative Analgesia

      While there are no data regarding the use of analgesics following repair of OASIS, a Cochrane review published in 2003
      • Hedayati H.
      • Parsons J.
      • Crowther C.A.
      Rectal analgesia for pain from perineal trauma following childbirth.
      found that rectal analgesia including diclofenac reduces perineal trauma related pain during the first 24 hours following birth and results in women using less additional analgesia during the first 48 hours. Because of the constipating effect of opioids, an NSAID in conjunction with acetaminophen is likely preferable as first-line management of perineal pain. Although rectal administration of NSAID may be better, it should be avoided in cases of fourth degree laceration, because it theoretically could impair.
      • McCarthy D.M.
      Mechanisms of mucosal injury and healing: the role of non-steroidal anti-inflammatory drugs.
      However, opioids should not be withheld, but rather used along with a stool softener.

      Recommendation

      • 8.
        Non-steroidal anti-inflammatories and acetaminophen are the first-line analgesics. Opioids should only be used with caution. Constipation should be avoided by using a laxative or stool softener. (1-A)

      Bladder Catheterization

      Studies have demonstrated a relationship between significant perineal trauma and postpartum urinary retention.
      • Yip S.-K.
      • Brieger G.
      • Hin L.-Y.
      • Chung T.
      Urinary retention in the postpartum period. The relationship between obstetric factors and the postpartum post-void residual bladder volume.
      • Ching-Chung L.
      • Shuenn-Dhy C.
      • Ling-Hong T.
      • Ching-Chang H.
      • Chao-Lun C.
      • Po-Jen C.
      Postpartum urinary retention: assessment of contributing factors and long-term clinical impact.
      • Glavind K.
      • Bjork J.
      Incidence and treatment of urinary retention postpartum.
      • Musselwhite K.L.
      • Fans P.
      • Moore K.
      • Berci D.
      • King K.M.
      Use of epidural anesthesia and the risk of acute postpartum urinary retention.
      Glavind and Bjork looked specifically at sphincter injuries and found sphincter rupture was observed in 33% of women with postpartum urinary retention compared with 1% of the total population of women giving birth during the study period.
      • Glavind K.
      • Bjork J.
      Incidence and treatment of urinary retention postpartum.
      The pathophysiology of postpartum urinary retention related to perineal injury is unclear but maybe related to perineal discomfort, urethral and perineal edema, and neurologic damage.

      Summary Statement

      • 4.
        Obstetrical anal sphincter injuries are associated with an increased risk of postpartum urinary retention. (II-2)

      RISK MANAGEMENT/DOCUMENTATION

      Operative delivery, while often indicated, is a risk factor for sphincter tear, and obstetrical care providers should consider discussing the possibility of operative delivery and any potential sequelae prior to labour. The decision for instrumental delivery should take into consideration the potential for anal sphincter injury. In addition, prolonged labour may be associated with sphincter tears and practitioners may consider discussing this with patients in situations when labour progression is slow.
      When faced with an OASIS, the obstetrical care giver should document (ideally as a formal operative note) the delivery course, including indication for operative vaginal delivery, consent obtained, description of procedure, type and extent of perineal injury, repair method and suture used, and antibiotics administered. Furthermore, the patient should be informed of the injury sustained, and upon discharge a follow-up plan should be made.

      Recommendation

      • 9.
        Following obstetrical anal sphincter injury, providers should disclose to women the degree of injury and arrange follow-up. Detailed documentation of the injury and its repair is required. (III-L)

      OUTCOMES FOLLOWING REPAIR

      The outcomes following the primary repair of obstetric anal sphincter injuries are difficult to establish as there is significant heterogeneity between studies. Studies vary greatly with respect to repair techniques, outcome measures, and follow-up intervals. A summary of outcomes following primary OASIS repair is presented in Table 5.
      • Sultan A.H.
      • Thakar R.
      Third and fourth degree tears.
      • Payne T.N.
      • Carey J.C.
      • Rayburn W.F.
      Prior third- or fourth-degree perineal tears and recurrence risks.
      • Dandolu V.
      • Gaughan J.P.
      • Chatwani A.J.
      • Harmanli O.
      • Mabine B.
      • Hernandez E.
      Risk of recurrence of anal sphincter lacerations.
      • Lowder J.L.
      • Burrows L.J.
      • Krohn M.A.
      • Weber A.M.
      Risk factors for primary and subsequent anal sphincter lacerations: a comparison of cohorts by parity and prior mode of delivery.
      Table 5Summary of outcomes from primary OASIS repair
      ReferenceRepair technique/injuryFollow-up Interval(s)Outcome measure(s)Prevalence mean (range)
      Sultan and Thakar 2009
      • Sultan A.H.
      • Thakar R.
      Third and fourth degree tears.
      (35 studies)
      End-to-end repair1–30 monthsAnal incontinence (flatal and/or fecal incontinence)39% (15 to 61%) (35 studies)
      Liquid or solid fecal incontinence14% (2 to 29%) (25 studies)
      Fecal urgency6% to 28%
      Sonographic anal sphincter defects34% to 91%
      Anal incontinence with coitus (flatal and/or fecal incontinence)17%
      Bagade and Mackenzie 2010End-to-end or overlap,6 monthsAnal incontinence11%
      n=79Fecal incontinence7.5%
      Tjandra et al. 2008End-to-end, n=11418.8 monthsFecal incontinence (Wexner>1)20.7%
      Samarasekera et al. 2008Unspecified, n=53>10 yearsOverall anal incontinence (Wexner>1)53%
      Flatal incontinence51%
      Incontinence to liquid32%
      Incontinence to solid26%
      The outcomes following OASIS repair appear to be related to the extent of the initial sphincter tear, with 3c or fourthth degree OASIS showing worse results than other types (see Table 6).
      • Roos A.M.
      • Thakar R.
      • Sultan A.H.
      Outcome of primary repair of obstetric anal sphincter injuries (OASIS): does the grade of tear matter?.
      • Berggren V.
      • Gottvall K.
      • Isman E.
      • Bergstrom S.
      • Ekeus C.
      Infibulated women have an increased risk of anal sphincter tears at delivery:a population-based Swedish register study of 250000 births.
      • Fernando R.
      • Sultan A.H.
      • Kettle C.
      • Thakar R.
      • Radley S.
      Methods of repair for obstetric anal sphincter injury.
      Table 6Outcomes following OASIS repairs according to the extent of the initial sphincter tear.
      ReferenceDegree of injuryType of repairFollow-up Interval(s)Outcome measure(s)Prevalence
      Nichols et al. 20054th, n=17unspecified6 to 8 weeksAnal incontinence and/or fecal urgency3rd: 28%
      3rd, n=394th: 59%
      Roos et al. 2010
      • Roos A.M.
      • Thakar R.
      • Sultan A.H.
      Outcome of primary repair of obstetric anal sphincter injuries (OASIS): does the grade of tear matter?.
      3a or 3b: n=439End-to-end or overlap8 to 12 weeksBothersome fecal incontinence or fecal urgency3c and 4th had worse scores on symptoms questionnaires than 3a and 3b
      3b or 4: n=92
      Any incontinence to liquid stool
      Fenner et al 2003
      • Fenner D.E.
      • Genberg B.
      • Brahma P.
      • Marek L.
      • DeLancey J.O.
      Fecal and urinary incontinence after vaginal delivery with anal sphincter disruption in an obstetrics unit in the United States.
      3rd and 4th,unspecified6 monthsWorsening bowel control after pregnancy4th: 30.8%
      n=1653rd: 3.6%
      Remote from delivery (median follow-up 14 years), the extent of sphincter damage was found to be independent of the development of fecal incontinence.
      • de Leeuw J.W.
      • Vierhout M.E.
      • Struijk P.C.
      • Hop W.C.
      • Wallenburg H.C.
      Anal sphincter damage after vaginal delivery: functional outcome and risk factors for fecal incontinence.
      Following OASIS, the incidence of anal incontinence may increase with time: from 3–6 months to 3–8 years following delivery, the rate went from 31% to 54%.
      • Wegnelius G.
      • Hammarstrom M.
      Complete rupture of anal sphincter in primiparas: long-term effects and subsequent delivery.
      Women’s continence over time may be affected by aging, subsequent deliveries, and lifestyle factors.
      Overall, the outcomes following the primary repair of OASIS are not encouraging, with studies reporting that many women suffer from various degrees of anal incontinence. Fortunately, the management of anal incontinence, including that following repaired OASIS, can be successful with pelvic floor physiotherapy.
      • Fynes M.M.
      • Marshall K.
      • Cassidy M.
      • Behan M.
      • Walsh D.
      • O'Connell P.R.
      • et al.
      A prospective, randomized study comparing the effect of augmented biofeedback with sensory biofeedback alone on fecal incontinence after obstetric trauma.
      • Mahony R.T.
      • Malone P.A.
      • Nalty J.
      • Behan M.
      • O'Connell P.R.
      • O’Herlihy C.
      Randomized clinical trial of intra-anal electromyographic biofeedback physiotherapy with intra-anal electromyographic biofeedback augmented with electrical stimulation of the anal sphincter in the early treatment of postpartum fecal incontinence.

      Recommendation

      • 10.
        Women with anal incontinence following obstetrical anal sphincter injury should be referred for pelvic floor physiotherapy. (I-A)

      SUBSEQUENT PREGNANCY

      Many factors may be taken into account in counselling women following an OASIS: the functional status (i.e. symptoms experienced shortly and remotely from the index delivery), the extent of residual anatomical and/or functional defects as shown on anal ultrasound and/or anal manometry, and the patient’s wishes.
      A woman who had an OASIS after her first delivery has 3.8- to 5.9-fold greater odds of a repeat OASIS at her next delivery than a woman without prior OASIS (Table 7).
      • Payne T.N.
      • Carey J.C.
      • Rayburn W.F.
      Prior third- or fourth-degree perineal tears and recurrence risks.
      • Dandolu V.
      • Gaughan J.P.
      • Chatwani A.J.
      • Harmanli O.
      • Mabine B.
      • Hernandez E.
      Risk of recurrence of anal sphincter lacerations.
      • Lowder J.L.
      • Burrows L.J.
      • Krohn M.A.
      • Weber A.M.
      Risk factors for primary and subsequent anal sphincter lacerations: a comparison of cohorts by parity and prior mode of delivery.
      • Parmar S.
      • Towner D.
      • Xing G.
      • Wallach S.
      Recurrent anal sphincter injury: a population based study.
      • Jango H.
      • Langhoff-Roos J.
      • Rosthoj S.
      • Sakse A.
      Risk factors of recurrent anal sphincter ruptures: a population-based cohort study.
      • Spydslaug A.
      • Trogstad L.I.
      • Skrondal A.
      • Eskild A.
      Recurrent risk of anal sphincter laceration among women with vaginal deliveries.
      • Peleg D.
      • Kennedy C.M.
      • Merrill D.
      • Zlatnik F.J.
      Risk of repetition of a severe perineal laceration.
      • Scheer I.
      • Thakar R.
      • Sultan A.H.
      Mode of delivery after previous obstetric anal sphincter injuries (OASIS)--a reappraisal?.
      Table 7Risks of OASIS at next delivery, based on presence of OASIS at 1st delivery
      OASIS at 1st deliveryNo OASIS at 1st delivery
      OASIS at subsequent delivery3.7% to 7.5%
      • Dandolu V.
      • Gaughan J.P.
      • Chatwani A.J.
      • Harmanli O.
      • Mabine B.
      • Hernandez E.
      Risk of recurrence of anal sphincter lacerations.
      • Lowder J.L.
      • Burrows L.J.
      • Krohn M.A.
      • Weber A.M.
      Risk factors for primary and subsequent anal sphincter lacerations: a comparison of cohorts by parity and prior mode of delivery.
      • Parmar S.
      • Towner D.
      • Xing G.
      • Wallach S.
      Recurrent anal sphincter injury: a population based study.
      • Jango H.
      • Langhoff-Roos J.
      • Rosthoj S.
      • Sakse A.
      Risk factors of recurrent anal sphincter ruptures: a population-based cohort study.
      • Spydslaug A.
      • Trogstad L.I.
      • Skrondal A.
      • Eskild A.
      Recurrent risk of anal sphincter laceration among women with vaginal deliveries.
      • Peleg D.
      • Kennedy C.M.
      • Merrill D.
      • Zlatnik F.J.
      Risk of repetition of a severe perineal laceration.
      • Scheer I.
      • Thakar R.
      • Sultan A.H.
      Mode of delivery after previous obstetric anal sphincter injuries (OASIS)--a reappraisal?.
      0.6% to 3.2%
      • Dandolu V.
      • Gaughan J.P.
      • Chatwani A.J.
      • Harmanli O.
      • Mabine B.
      • Hernandez E.
      Risk of recurrence of anal sphincter lacerations.
      • Lowder J.L.
      • Burrows L.J.
      • Krohn M.A.
      • Weber A.M.
      Risk factors for primary and subsequent anal sphincter lacerations: a comparison of cohorts by parity and prior mode of delivery.
      • Spydslaug A.
      • Trogstad L.I.
      • Skrondal A.
      • Eskild A.
      Recurrent risk of anal sphincter laceration among women with vaginal deliveries.
      • Peleg D.
      • Kennedy C.M.
      • Merrill D.
      • Zlatnik F.J.
      Risk of repetition of a severe perineal laceration.
      Although higher than in women without a prior OASIS, the risk of having a recurrent OASIS is the same for a woman with previous OASIS as the baseline risk at first delivery; both around 5.3% in Ontario.33 The vast majority of women with a previous OASIS will not have a recurrent OASIS during a subsequent vaginal delivery. In fact, 64% to 90% of all OASIS occurring at a second delivery are in women without a previous OASIS.
      • Spydslaug A.
      • Trogstad L.I.
      • Skrondal A.
      • Eskild A.
      Recurrent risk of anal sphincter laceration among women with vaginal deliveries.
      • Peleg D.
      • Kennedy C.M.
      • Merrill D.
      • Zlatnik F.J.
      Risk of repetition of a severe perineal laceration.
      Overall, the rate of anal incontinence in women with OASIS and a subsequent vaginal delivery worsens in 19% to 56% of women,
      • Poen A.C.
      • Felt-Bersma R.J.
      • Strijers R.L.
      • Dekker G.A.
      • Cuesta M.A.
      • Meuwissen S.G.
      Third-degree obstetric perineal tear: long-term clinical and functional results after primary repair.
      • Bek K.M.
      • Laurberg S.
      Risks of anal incontinence from subsequent vaginal delivery after a complete obstetric anal sphincter tear.
      • Tetzschner T.
      • Sorensen M.
      • Lose G.
      • Christiansen J.
      Anal and urinary incontinence in women with obstetric anal sphincter rupture.
      • Faltin D.L.
      • Sangalli M.R.
      • Roche B.
      • Floris L.
      • Boulvain M.
      • Weil A.
      Does a second delivery increase the risk of anal incontinence?.
      particularly if a women had transient anal incontinence after the index OASIS.
      • Bek K.M.
      • Laurberg S.
      Risks of anal incontinence from subsequent vaginal delivery after a complete obstetric anal sphincter tear.
      On the basis of these studies, the Royal College of Obstetrics and Gynaecologistsis recommend that “All women who have sustained an obstetric anal sphincter injury in a previous pregnancy and who are symptomatic or have abnormal endoanal ultrasonography and/or manometry should have the option of elective Caesarean birth.”
      • Royal College of Obstetricians and Gynaecologists
      A 2003 study using a decision analysis modeling explored universal Caesarean section in continent women with previous OASIS.
      • McKenna D.S.
      • Ester J.B.
      • Fischer J.R.
      Elective cesarean delivery for women with a previous anal sphincter rupture.
      Based on the literature, they used the following assumptions: 5.1% risk of repeat OASIS, anal incontinence rate of 44% after 2nd OASIS. To prevent one case of anal incontinence (flatus, liquid, or stool) in women with prior OASIS who were presumed continent 2.3 elective Caesarean sections would need to be done, at the cost of increased maternal risks, including an increased morbidity rate from 4.2% following vaginal delivery to 11.3% after Caesarean section. Furthermore, there would be one maternal death for 1880 cases of anal incontinence averted. The balance of risks and benefits should be discussed when counselling women on the route of future deliveries after OASIS in a previous pregnancy.

      Outcome of Subsequent Vaginal Delivery Depending on Symptoms Following OASIS at Index Delivery

      Only one published study assessed anal symptoms in women with a subsequent delivery based on their symptoms after the index OASIS.
      • Bek K.M.
      • Laurberg S.
      Risks of anal incontinence from subsequent vaginal delivery after a complete obstetric anal sphincter tear.
      Women who sustained a fourth degree tear in a previous delivery associated with transient anal incontinence had a greater rate of developing subsequent anal incontinence after a subsequent vaginal delivery (39%, 9/23; 4 of these women became permanently incontinent compared with 7% [2/29] of asymptomatic women after their OASIS). In a recent preliminary report, low baseline symptom scores may predict good outcomes after a vaginal delivery in women with prior OASIS.
      • Jango H.
      • Langhoff-Roos J.
      • Sakse A.
      Does mode of second delivery after obstetric anal sphincter rupture influence the risk of anal incontinence?.

      Outcome of Subsequent Vaginal Delivery Depending on Finding on Endoanal Ultrasound Following OASIS at Index Delivery

      The literature is limited in number and size of studies, but the presence of a persistent defect appears to increase the risk of worsening symptoms. In women who had ultrasound evidence of anal sphincter injury 3 months following a first vaginal delivery (any degree of tear), a subsequent vaginal delivery may increase the rate of abnormal anorectal symptoms (38%), compared with women who did not have another child (16%; not statistically significant). Women without ultrasound evidence of OASIS 3 months postpartum had a rate of anal incontinence of 3% in the absence of a subsequent pregnancy versus 10% if they delivered again (not statistically significant).
      • Faltin D.L.
      • Sangalli M.R.
      • Roche B.
      • Floris L.
      • Boulvain M.
      • Weil A.
      Does a second delivery increase the risk of anal incontinence?.
      In women who have a second vaginal delivery, the presence of anal injury on antenatal ultrasound between deliveries increases the rate of worsening anorectal symptoms: from 7% of women following a subsequent vaginal delivery without evidence of persistent defect, to 37% if ultrasound showed a pre-existing injury (no significant difference).
      • Mahony R.
      • Behan M.
      • O’Connell P.R.
      • O’Herlihy C.
      Effect of second vaginal delivery on anal function in patients at risk of occult anal sphincter injury after first forceps delivery.

      Outcome of Subsequent Vaginal Delivery Depending on Combined Finding on Endoanal Ultrasound and Anal Manometry Following OASIS at Index Delivery

      Sultan reported his results following antenatal counselling for the route of delivery in subsequent pregnancy for women with previous OASIS,
      • Scheer I.
      • Thakar R.
      • Sultan A.H.
      Mode of delivery after previous obstetric anal sphincter injuries (OASIS)--a reappraisal?.
      with updated results presented in 2013.
      • Daly J.O.
      • Sultan A.H.
      Van delft KW, Thakar R. Outcome of childbirth after previous obstetric anal sphincter injury. 38th Annual Meeting of the International Urogynecological Association, IUGA.
      In his study, substantial anal compromised was defined as either:
      • external sphincter defect on ultrasound >30° and a maximum squeeze pressure increment of <20 mmHg on anal manometry;
      • OR
      • defect <30° and a maximum squeeze pressure increment of <20 mmHg;
      • OR
      • no defect and a maximum squeeze pressure increment of <20 mmHg.
      Women who had substantial anal compromise were counselled on having a Caesarean section. All others were counselled on vaginal delivery. In those women who delivered as counselled (75% of the study group), results on anal manometry did not significantly change and anorectal symptoms did not worsen following delivery. Similar results have been presented as abstracts.
      • Karmarkar R.
      • Bhide A.A.
      • Digesu A.
      • Khullar V.
      • Fernando R.
      Mode of delivery after previous obstetric anal sphincter injuries (OASIS)-a prospective observational study.

      Summary Statements

      • 5.
        After a successful repair of obstetrical anal sphincter injuries, most women can safely deliver vaginally in a future pregnancy. (III)
      • 6.
        Counselling women about future delivery plans:
        • a.
          The risk of recurrence of an obstetrical anal sphincter injuries at a subsequent delivery is 4% to 8%. (II-2)
        • b.
          It was calculated that 2.3 Caesarean sections at the cost of increased maternal risk would be required to prevent one case of anal incontinence in a woman with prior obstetrical anal sphincter injuries. (II-2)

      LEARNING MODEL

      For the past decade, Sultan and his group has devised a hands-on workshop on OASIS repair. The hands-on part uses both an artificial model and a repair of fresh anuses originating from male pig.
      • Andrews V.
      • Thakar R.
      • Sultan A.H.
      Structured hands-on training in repair of obstetric anal sphincter injuries (OASIS): an audit of clinical practice.
      It has been shown that a surgical skill laboratory improves learners’ acquisition of the skills necessary to repair OASIS as evidenced on the Objective Structured Assessment of Technical Skills and written examination administered before and after an OASIS repair workshop.
      • Siddighi S.
      • Kleeman S.D.
      • Baggish M.S.
      • Rooney C.M.
      • Pauls R.N.
      • Karram M.M.
      Effects of an educational workshop on performance of fourth-degree perineal laceration repair.

      SUMMARY

      Obstetrical anal sphincter injuries represent a significant morbidity encountered after vaginal delivery. Some intrapartum measures can be taken to diminish the risk of occurrence. Careful examination after every delivery is of paramount importance to avoid missing an OASIS. Systematic repair of the entire anal sphincter complex should be done by a trained caregiver; full disclosure and close follow-up should be offered. Most women following OASIS are good candidates to have a subsequent vaginal delivery; antenatal evaluation of symptoms and anal function testing can help guide the choice of future mode of delivery.

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